Process of purifying and dehydrating switch oil



July 3, 1.923.

C. H. HAPGOOD PROCESS OF PURIFYING AND DEHYDRATING SWITCH OIL Filed May5 1921 \\\\x\\\\\\\\\\\\ I- 6 Q r42 gram fi ward/r cyvyaao Patented July3, 1923.

UNITED STATES I 1,460,718 PATENT OFFICE.

C YBUS HOWARD HAPGOOD, OF NUTLEY, NEW JERSEY, ASSIGNOR TO THE DE LAVALSEPARATOR COMPANY. OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

PROCESS OF PUBIFYING AND DEHYDRATING SWITCH OIL.

Application filed May 3, 1921.

To all whom it may concern:

Be it known that I, CYRUs ,HOWARD HAP- coon, a citizen of the UnitedStates, residing at Nutley, county of Essex, and State of New Jersey,have invented a new and useful Improvement in Processes of Purifying andmerse electric switches in oil in order to avoid the formation orpersistence of destructive arcs. This is especially true where theamperage is so high that the blowring out of the arc could not beeffected by a magnet or other known means and when, therefore, therewould be a destructive burning of the switch contact points.

After each use of the oil there is more or less breaking down of the oilinto carbon, a large part of which is colloidal carbon. After repeatedoperations of the switch, the accumulation of carbon becomes so greatthat the oil is unfit for further use. There is, also, more or lesscontamination of the oil by dirt and water. While the percentage ofwater that is absorbed by the oil is very small, the presence of anamount of water so small as to be negli ible for most uses for which oilis ava1la%le is objectionable in switch oil, as it seriously reduces itsdielectric strength. a

Water cannot be wholly separated from oil by gravity. Where 011 containsa substantial percentage of water, prolonged settlement will yield anoil that contains approximately only one-quarter of one per cent ofwater. For many purposes this degree of purification suffices. Where astill further purification is desired, it may be effected bycentrifugation. Centrifugation may be effected in any machine of thecream separator type, wherein the water will escape from one outlet andthe oil from the other. However, the percenta e of water that willresist elimination y gravity treatment is far greater than suffices, inswitch oil, to so lower its dielectric strength so as to render it unfitfor use, while the specified centrifugal treatment, when con ducted inthe most effective type of centrifuge specified, yields an oil ofscarcely greater dielectric strength than switch 011 Serial No. 466,496.

that has been contaminated to a permissible degree by prolonged use. Inother words, used switch oil requiring purification and dehydrationcontains far less moisture than oil after it has been dehydrated to thegreatest extent possible by gravity, while the specified centrifugaltreatment is ineffective to reduce the proportion of water to the almostabsolute degree required to meet the requirements for fresh switch oil.

To urify switch oil, resort is usually had to a lter press comprisingapproximately 1000 sheets of blotting paper, through which the oil isforced. The blotting paper takes up practically all the water as well asthe carbon, and any particles of dirt. The process is fairlyexpeditious, as it purifies about thirty gallons per hour.

However, the process is open to serious objections. Minute shreds ofblotting paper are found suspended in the otherwise purified oil andthese particles tend to accumulate on the switch surfaces. Moreover,after each operation, a certain percentage of the paper units are foundto be so torn and broken as to require replacement. My own observationshows that often as many as one-third of the sheets of paper are soimpaired or destroyed. Their constant renewal is an item of someexpense, as is also the labor required to eifecttheir replacement.

The object of my invention is to provide a more expeditious method ofpurification, whereby the results secured, with respect both to removalof carbon and dirt, and elimination of water, will be at least assatisfactory as those secured by the blotter filter, and whereby theexpense of labor and material required for upkeep will be practicallyeliminated.

In the first step of my process I utilize a process the same as, orsimilar to, that set forth in my Patent No. 1,363,784, dated December28, 1920, That is, to one hundred gallons of oil I add about threepounds of a readily saponifiable oil, such as any of the glyceride, ormore preferably oleic acid (red oil), which is miscible in allproportions with the mineral oil usually used. While maintaining thesolution heated I add an alkaline solution (say about one and onehalfpounds of soda ash) of a sufiicient concentration to completely saponifythe oleic acid and form a counter colloid, which takes up the colloidedcarbon suspended in the oil.

I may also add a suitable salt (say about one and one-half pounds ofsodium chlorid or sodium sulfate) to facilitate separation and preventthe formation of an emulsion. The soda ash, or soda ash and salt (if thelatter be used) should be dissolved in about nine gallons of water.

I then apply centrifugal force to remove from the lighter oil theheavier saponified matter or soap solution and the previously suspendedcarbon and dirt that have been transferred from the oil to the soapsolution.

I prefer to use a centrifugal separator of,

the type shown in the'Snyder Patent No. 1,283,343 of October 29, 1918,such as a machine being especially available where it is desired toseparate from a light liquid heavier impurities comprising one or moreheavier liquids and one or more solids.

Less desirably, the oleic acid and alkali ma be dissolved in water toform a soap an the soap. thus formed added to the switch oil and the oilthen centrifuged. Or prepared soaps, such as Gold-Dust, may be used. Thepreferred procedure, however, wherein the soa is formed in the body ofthe switch oil, is more efiicient, in that it insures a very intimatepreliminary admixture of the saponifiable oil with the mineral oil,thereby insuring, after the addition of the alkali, that the countercolloid formed by the resultant soap will take up every particle ofsuspended colloidal carbon.

The process above described gives an oil which is free from carbon anddirt, and con. tains so little water that it would normally beconsidered substantially dehydrated, being adapted to most purposes forwhich oil is used; but it is not comparable with the product of thedescribed filter press in that it still contains too much water to adaptit for use as switch oil. Indeed, owing to the addition of waterinvolved in the treatment with a water solution of an alkali and asaponifiable oil, the partially purified oil may contain slightly morewater than before treatment.

To further dehydrate the partially purified oil, I then subject the oil.to centrifugal force under conditions which will insure the eliminationof a large part of the remaining water. Preferably centrifugal force isapplied while continuously introducing fresh quantities of the oil andproviding for the continuous outflow of the dehydrated oil and confiningfrom escape the water which is carried to the periphery, so that itbuilds up an envelope of gradually increasing thickness as the operationproceeds. This step of the process is preferably carried out in aseparator of the Snyder type specified, but modified by sealing thedischarge for the heavy liquid, as set forth in another applicationfiled by me Mayo, 1921, Serial No. 466,962.

The second step of the process may also be carried out in an ordinarycream separator having a liner of the known multiple disc t pe, provideda water seal for the heavy liqui discharge outlet is initiallyestablished; but with such a separator the maximum degree of dehydrationis not obtainable, because the oil is not initially distributedthroughout the peripheral portion of the bowl so as to insure thesubjection of all the oil to the maximum centrifugal force.

Both steps of the processmay also be carried out in a single chamberopen bowl clarifier, which is intended primarily for the separation ofsolid ingredients from a liquid. If such a bowl is used for carrying outmy process, the water will tend to be forced out toward the peripheryand remain there, but a very small proportion of the water will flow outwith the oil. While, in

' the second step of the process, the maximum dehydration will exceedthat obtainable with a cream separator of the multiple disc type, itwill not meet the exacting requirements of high voltage limits.

modified as described, provision is made, 1n the dehydrating step of theprocess, for initially distributing the oil throughout the peripheralpart of the bowl, and the multiple disc liner divides the bowl into amultiplicity of separating compartments, wherein the oil is subjected tobe repeated centrifugations, showing the elimination of the maximumpercentage of water before the oil is free to escape. Moreover, thesediscs With a separator of the Snyder type,

afford'a large area for catching and holding an impurities, such, forinstance, as partic es of dirt, or fine shreds of blotting paper thathave been carried off by oil that has previously been dehydrated byfiltration through a filter of the blotter press type. 'VVhile, at theend of the process, all the water in the total quantity of oil treatedremains in the separator bowl, so little water is left in the oil afterthe first centrifugal treatment that the thickness of the surroundingwall of water at the end of the second centrifugal treatment is notsufficiently great to materially reduce the bowl volume available forseparation.

It is found more economical to use the same separator for bothcentrifugating steps and leave open the discharge for the heavierliquids and solids in the first step and seal the discharge in the iaststep. Thus the necessity for buying two separatlng machines is avoided.

By my process I can purify one hundred gallons of switch oil per hour,or over three times the amount purifiable by means of the filter press.The approach to absolute dehydration, where the second step of theprocess is carried out in preferred manner described, is even morenearly cbmplete,

tests showing the oil to have a dielectric strength of 53,000 volts ascompared with 47,000 volts when filtered. The carbon and dirt are atleast as completely removed and there is, of course, no carrying off ofminute shreds of blotting paper. There are no elements in the separatorrequiring replacement after use, the expense of upkeep being negligible.

I have heretofore stated that my process is not dependent for itsexecution on any particular types of centrifuge. I have mentioned thatthe first centrlfugal step of the present process may be carried out ina bowl the second step may be carried out in a .similar bowl with thedischarge for the heavy liquid sealed, as disclosed in my Patent No.1,422,856, issued July 18, 1922. In the drawings I have shown a mosteflicient and convenient bowl of the Snyder type, with means to seal thedischarge for the heavy liquid, and which can be adapted to carry outboth steps of my process, the same being specificallIyIdisclosed in apatent granted to Selden H. 852.

Fig. 1 is a vertical section through the bowl when adapted to functionas a separator or purifier. Fig. 2 is a vertical section through thebowl when adapted to function as a clarifier.

In both views, a is the supporting rotary spindle, b the bowl body, athe bowl top, 0? the ring by which the bowl top is secured to the bowlbody, e the central feed tube, f radial channels leading from thecentral feed tube to the separating space of the bowl, 9 the linercomposed, as usual, of a all, July 18, 1922, No. 1,422,-

T number of superposed discs, and vanes or wings h for compelling theliquid near the periphery to rotate with the bowl. In each bowl there isa top disc above the liner.

In the'separator or purifier (Fig. 1) the top disc m is provided with aneck n having an internal discharge weir 0, while a weir p, having adiameter slightly eater than. the outside diameter of the neo issecured, by means of a" flanged ring 1', to the upper end of thebowltop. The lower end of the top disc extends substantially outside theliner g, overhanging the free space between the liner and the bowlperiphery, and terminates a relatively short distance from suchperiphery, leaving a space .9 outside and above its edge, around whichthe heavier liquid escapes into the conduit between the top disc and thebowl to To convert the centrifuge into a clarifier, the top disc m andweir p are removed and there are substituted atop disc u and weir o, asshown in Fig. 2. The weir o is of a diameter not greater than, andpreferably the same as t e diameter of the weir 0. The top discs at isunprovided with a neck and its central opening is of somewhat greaterdiameter than that of weir 'v. The lower end of the top disc u isprovided with a ring or enlargement t, which rests against, or closelyapproximates, the cover of the bowl, thereby blocking or substantiallyobstructing the outflow of liquid from the peripheral part of the bowlinto the space above the top disc;

In the first centrifugal step of my process, when carried out in. thepurifier of Fig. I, a mixture of soap solution and carbon flows outaround the lower edge of the top disc m, fills the conduit above the topdisc and discharges over the neck of the bowl. The lighter liquid,containing a very small percentage of heavier-liquid, mostly water, isdisplaced inward, flows upward inside the neck a of the top disc m andis discharged over the neck. The process may be repeated if thepercentage of heavier liquid is greater than is practicable to permitthe successful execution of the final step.

In the final step of my process, when carried out in the clarifier ofFig 2, there is fed into the bowl the contaminated oil that has beenseparated out in the preceding step of the process. I state that the oilis contaminated, although for man purposes it would be regarded as pure.ut for switch oil, its condition has merely been changed by the firstcentrifugal process, from one state of impurity to another state ofimpurity. That is, ori inally the impurity consists of water an carbon.Prior to the last step the impurity consists of soapy water with thecarbon practically eliminated, although what slight proportion mayremain has been taken up by the soap. The small proportion of soa ywater present is thrown to the perip cry of the clarifier, where itaccumulates and forms an envelope of gradually increasing thickness. Thelighter liquid is continuously discharged over the weir. This lighterliquid is the practically absolutely pure oil which it is the object ofmy process to secure.

Having now fully described my invention, what I claim and desire toprotect by Letters Patent is l. The process of purifying and dehydratingoil containing carbon and water, such as switch oil, which comprisesforming a. mixture of the oil with soap, subjecting the mixture tocentrifugal force to eliminate the carbon, dirt, soap and a large partof the water, and subjecting the thus partially purified but imperfectlydehydrated oil to centrifugal dehydration.

2. The process of purifying and dehydrating oil containing carbon andwater, such as switch oil, which comprises forming a mixture of the oilwith soap, subjecting the mixture to centrifugal force to eliminate thecarbon, dirt, soap and a large part of the water present in the mixture,subjecting the thus partially purified but imperfectly dehydrated oil tocentrifugal force and during the centrifugal operation admitting freshquantities of oil and allowing the outflow of oil from which the waterhas been eliminated while confining the water from escape so as to buildup a surrounding water envelope of gradually increasing thickness.

3. The process of purifying a liquid containing solid and relativelyheavy liquid impurities in relatively small proportion, which comprisesadding a liquid heavier than the liquid to be purified, eliminating thesolid impurity andmost of the heavier liquid by centrifugal force, andeliminating practically all the remaining heavy liquid from thepartially purified light liquid by subjecting the same to centrifugalforce and during the centrifugal operation admitting bon taken up. bythe soap are discharged simultaneously with and separately fro-m thelighter oil, while in the last centrifugal operation, which is appliedto the thus separated but imperfectly dehydrated oil, the lighterliquid, namely: the oil, is allowed to discharge, while the smallproportion of heavier liquid is restrained from discharge and allowed tobuild up a surrounding film or envelope of slowly increasing thicknessas the operation proceeds.

In testimony of which invention, I have hereunto set my hand, at NewYork, on this 28th day of April, 1921.

CYRUS HOWARD HAPGOOD.

Witnesses: 7

JOHN G. PAUL, HERBERT R. WILLIAMS.

